Bad cast involving variant datatypes

[fabiomadge]

Running the compiled version of this program results in a failed cast. The cast is emitted to support the match statement.

datatype X<+U> = X(x: U)

trait Tr {}
class Cl extends Tr {
    constructor () {}
}

method Main() {
    var cl := new Cl();
    var e: X<Tr> := X(cl);
    match e
    case X(tr) => return;
}